UPDATE: This might be a little harder than we thought. We asked Lady Ada if an RF jammer could in fact be used in this way. She says, “it can, however there are multiple RFID frequencies so youd have to pick out VCOs to match.”

RF jammers are illegal in the US and subject to FCC fine.

(m) Harmful interference. Any emission, radiation or induction that endangers the functioning of a radio navigation service or of other safety services or seriously degrades, obstructs or repeatedly interrupts a radiocommunications service operating in accordance with this Chapter.

Which includes:

(p) Kit. Any number of electronic parts, usually provided with a schematic diagram or printed circuit board, which, when assembled in accordance with instructions, results in a device subject to the regulations in this Part, even if additional parts of any type are required to complete assembly.

Furthermore

The operation of transmitters designed to jam or block wireless communications is a violation of the Communications Act of 1934, as amended (“Act”). See 47 U.S.C. Sections 301, 302a, 333. The Act prohibits any person from willfully or maliciously interfering with the radio communications of any station licensed or authorized under the Act or operated by the U.S. government. 47 U.S.C. Section 333. The manufacture, importation, sale or offer for sale, including advertising, of devices designed to block or jam wireless transmissions is prohibited. 47 U.S.C. Section 302a(b). Parties in violation of these provisions may be subject to the penalties set out in 47 U.S.C. Sections 501-510. Fines for a first offense can range as high as $11,000 for each violation or imprisonment for up to one year, and the device used may also be seized and forfeited to the U.S. government. (FCC website)

Yes, these jammers are fantastically illegal here in the states. Our best bet currently is to simply avoid RFID cards, and make clear to anyone who will listen that, until there’s at least nominal security in place, we don’t want them.

My favorite (theoretical) RF jammer is the short radius cell phone RF jammer, which can bring a quick (and satisfying!) end to the inane prattle surrounding you on the train/bus/restaurant/etc. They’re available all over the place online, and I’m endlessly tempted…

What about wrapping the cards in tinfoil — would that work? I seem to remember that was a suggestion in a previous RFID chip discussion. I have no idea whether it would be effective or not, though. I forsee a time when it won’t be possible to get a card without RFID, unfortunately.

Actually, you don’t have a choice anymore with HSBC.
When geting a replacement ATM card from HSBC (the mag strip wore out), it came with the shiny new paypass feature. When i called them up to request one without (like the card i was replacing) they said that it is not offered, even at the customers request!

At a gas station/truck stop I found this nifty stainless steel “cigarette case” – too small for cigarettes, but exactly the right size for my credit card. It is designed like a cig-case since it has spring-loaded clips to keep things inside when it is opened.

I don’t have any RFID credit cards, but do have a stick-on for “zip thru” at work. Yet this case should work like multiple layers of foil (it seems to for my existing keycards which use RFID, though I should do a better test).

If this technology is easily exploited it will either be modified or discontinued as it will end up costing credit card companies more money to manage the stolen credit card accounts. I’m really not losing sleep over this one.

Yeah, Chase doesn’t give you a choice. I’ve got a RFID blocking wallet on order and it can’t get here fast enough. NYC has enough physical pickpockets, I’d like to keep it at least that challenging to get my card.

I work in RFID development and to read data from a tag from anywhere other than a very short distance takes a fairly substantial system than would be hard to conceal and the use of it would be pretty obvious. Assuming you were paranoid about it all you would have to do is put foil in your billfold or better yet mu metal. This kind of equipment is much more complex that those tags that alarm when you leave Walmart or somewhere like that.